Bituminous paving composition and method of preparing the same



Units Patented Feb. 17,1931

Enwin c. wALLAcn'or NEWTON, MASSACHUSETTS BIrtrMiiioUsrAvInG coMrosrrroNaim METHOD FPREPARIiNG1HE SAME 7 No Drawing.

This invention relates to bituminous paving compositions and the methodof prepar- 7 ing the same, andhas for its object the propense.

'gatile solvent is used combined directly with the bitumen or applied tothe stone before the addition of the bitumen, but thus far such ductionof a paving mixture prepared by the hot mixed method WlllCllmaybe laidimmediately after mixing or kept for anindeterminate time and laid cold;

In the construction of bituminous pavements-experience has'shown thatthe best results can be assured only by the use of bituprepare mixturesworkable at atmospheric temperature chiefly by means of cut back?compositions of various types, in which a volpractice has met only withindifferent suc- 1 cess, even upon roads whereon the traffiois 7 light.It is an ob ect of this invention to prepare a paving mixture by the"hot mixed method which maybe laid either hot or cold with equallyassured success; This is accomplishedby thoroughly mixing; heatedmineral aggregate of any desired type (coarse or fine aggregate) withheated bituminous cement to form an agglutinated mass,

*then immediately converting it into a noncoherent granular and friablecondition by adding'thereto and conimingling therewith a cold finelydivided composition consisting of an intimatecombination of mineralmat-7' ter and bitumen which composition may be either naturalorespecially prepared. The

cold compositionis added in suflicient quan- V ftity to preventagglomeration of'the'heatedmass, if the latter is chilled withoutbeingcompressed. -This'cold composition as added possesses certain qualitieswhich particularly adapt it to the purpose. It is moisture free and isreadily miscible in all proportions with oily or bituminous compositionsofa-ny' natu'minous mixtures, I I i i p The-method of preparing, theimproved Application filed April 23, 1927. serial in; 186,171;

ture. Although in a granular or pulverulent condition probably due tothequantity and quality of the bituminous content, it can be Iconsolidated readily into a firm coherent body without other treatmentthan theapplication of'pressureiand when'added in proper proportion to ahot mixture of bitumen: and mineral matter imparts the same propertiesthe theentir'e mass. That, is to say, the hot,

gummy, unwieldly mass-is" converted intoa' granular, friable'materialeasily workable at atmospheric temperature and compressible into afirmly coherent' mass by any oftlie methods usually employed incompacting biinvention is as follows I The mineral aggregate, whichmaybe of any desired type either coarse or fine; is J heated toate'mperature ranging from 220 to L25" Fahrenheit, and aficarefullyweighed paving composition in accordance with this portion is combinedin a suitable mixer with v 5 heated asphalt cement of the desired. fconsstency, ranging according to conditions off "use from to 150 penetrationonany of the standard penetrationmachines now in general use; Sulfieientof the asphalt is I used to thoroughly coat eachof'the particles of theaggregate the amount" usually 80" required ranging ffromf l %fito' 15%of the weight of the mineral I aggregate according to its character.IAfter the'heated mineral aggr g e and the heated bituminous ce- 7@1613; have been thoroughly mixed; the cold v Q granular composition ofmineral inatterand bitumen addedyandtlie minin'g zcontinued v until thec'old' icomposition istl oroughly distributed throughout the entire massandbetween the coated oarti'cles'of the ag regate. Themixture as agwholeloses its and I sticky character an'd becomes more i or lessgranular-andsubstantially non-coherent 'until it is subjected topressure or-is compacted by any'of the usual methods; vThe amount of-thecold-granular bituminous composition 'requirednaturally 'variesiwiththecharacter i "of the mineral aggregate of the hot mixture,

-froni'5%' to 20% being generally sufiicient for: a coarse aggregateinixture, but 'i'n fine streets-and reduced to powder more or less jcoarse, and if need be in some instances addlng thereto more bitumen ormore flux. It may then be used as the granulatlng medium heated mixture'when it becomes chilled.

Such material as here referred to may be embraced in the expressioncold, finely divided bitumen-containing composite material 'as used incertain of the appended .claims.

The term bltuminous as used 1n the appended claims is intended to coveriasphaL .tic as well, since asphalt is to be considered as a specifickindof bituminous .mat'erial.

example, there V able but susceptible of consolidation into a firmlycoherent mass by the application of pressure alone. V I

In testimony whereof I afiix my signature;

EDWIN G. WALLACE.

'to prevent balling oragglomeration of the 7 After the cold granularcompositionihas been incorporated into'it, the mixture may be hauled tothe street and laid the same as any hot mixed paving mixture, as it willbe found to be free working. Or, the mixture as a whole may'be storedand used as required without the necessity for reheating it at any time.tures above F. and can be handled in a temperature as low as 30 F. i

.What I claim is y 1. The method of preparing bituminous pavingcompositions workable at atmos; v pheric temperature which comprises thecoat- It is free working at all te1npera-- ing of heated particles ofmineral'matter with heated bituminous cement in sufficient I quantity tocause agglomeration when the mass becomes chilled','but prior tochilling, adding to said mass a quantity of cold, noncoherent,non-hygroscopic composition co1n 1 prising mineral particles coated withbituminous cement, the latter composition 1n 1 quantity beingsuflicientto render the entire mass granular and'friable butsusceptible-of 2'. The method of preparing bituminous 5 pherictemperature which comprises the mixfoo ing ofheated mineral mattera'nd'heated consolidation into a'firmly coherent mass by j p a 1 theapplication of pressure alone.

. ,paving compositions workable at' atmosbituminous cement insufficientquantity to r g V 1 form an agglutinated mass,,thenaddingthereto a previously prepared'compositionf consisting of oldpaving mixtures reduced-p to a coarse powdery condition and contain- 7ing bitumen and mineral matter, the quantity of'the lattercompositionbeingsufficient :to render the entire mass granular andv fri-

